Project Summary - Project 2 The extracellular matrix (ECM) is a key component of the prostate cancer (PC) tumor microenvironment. Work in Project 2 addresses the function of a key heparan sulfate proteoglycan, perlecan (PLN)/HSPG2, found in the basement membrane and reactive stroma of prostate and bone, that possesses both structural and signaling functions. Metastatic PC cells must cross five PLN-rich ECM layers to travel from the prostate to colonize bone. Despite its considerable size and complexity, PLN's basic architecture is evolutionally conserved. PLN's tandem, functional domains both promote and prevent basic biological responses such as adhesion, migration, angiogenesis, and inflammation. The molecular switch depends on context, specifically whether the proteoglycan is intact or degraded by matrix metalloproteinases such as MMP-7/matrilysin to produce bioactive fragments. Additional activity arises from the actions of enzyme modifiers of HS chains on PLN domain I, including heparanase (HPSE) and sulfatases (SULFs). This diverse activity promotes wound healing in normal tissues, but is co-opted by PC cells to facilitate metastasis and disease progression. Work in Project 2 focuses on domain I, which plays a key role in delivery of heparin binding growth factors, and domain IV, which acts as a barrier that when degrades participates in tumor dyscohesion and epithelial mesenchymal transformation (EMT). With Project 1 of this program, we showed that a domain IV fragment actively participates in formation of Metastasis Initiating Cells, or MICs. Each of the proposed experiments leverages existing resources in the PO1, but answers new, broadly-relevant questions regarding the role of PLN in PC progression, invasion, and metastasis. Our Rice team contributes uniquely to this PO1 group by bringing fundamental studies of proteoglycan catabolism and signaling in two integrated Aims, elements of tumor bioengineering in bilayer design and fabrication to facilitate the larger aims of the PO1 group including growing circulating tumor cells and disseminated tumor cells from all three projects in 3D, and the potential to develop a signature for invasion and metastasis that can contribute to a larger understanding of the underlying biological factors that determine which PC patients are likely to suffer rapid disease progression and thus should be treated more aggressively earlier. Synergy is found in our application of resources from all four PIs' laboratories and the two program Cores, particularly in the translational potential for PLN or its fragments as diagnostic tools to predict patients likely to progress rapidly to lethal disease.